1. Field of Invention
The present invention relates to hoisting and handling systems and methods. More particularly, the present invention relates to a system and method to facilitate the hoisting, positioning, installation and removal of continuous track drive units.
2. Description of Prior Art
Continuous track drive units are used in many types of vehicles and machinery including tractors, construction equipment, and military vehicles. Because continuous track drive units have no beginning or end, installation is often difficult and cumbersome given the need for precise positioning and alignment with respect to the vehicle hubs. Furthermore, because continuous drive track units are not stretchable, the continuous track drive unit must be held taut and in a configuration nearly identical to that of an installed track prior to installation. Such requirements add greatly to the difficulty in installing and removing continuous track drive units.
Another consideration is the weight of the continuous track drive unit. Often, track drive units are constructed with closely spaced steel cables running parallel to the circumference. The steel cables are sheathed in a cast tread, while rubber cogs are cast into the inside circumference to keep the continuous track drive unit captive and centered on its support and drive idlers. These components render continuous track drive units heavy and awkward to manipulate. Nonetheless, these limitations must be overcome when continuous track drive units are installed on vehicles.
Continuous track drive units are commonly shipped positioned on their sides in closely fitted crates. It is advantageous to remove the continuous track drive unit without damage to the unit itself or to the crate. However, using presently available methods, removal of the continuous track drive unit is typically accomplished using multiple chains or wire rope or synthetic slings, and considerable physical strain is required to position these around the track, before it can be lifted from its crate with a suitable hoist. Tong style gripping clamps may also be used to grip the track, thereby eliminating the strain of manipulating the track over chain or sling rigging. Because the purpose this style clamp serves is very specialized, these clamps are not readily available in the field. Furthermore, the balancing of stresses applied to multiple clamps by the manner in which they are rigged to the hoisting device is easily misjudged, increasing the risk of damaging the track. A method is clearly needed, which this invention provides, to securely and quickly lift the continuous track drive unit from its crate, to even begin dealing with it, that offers no potential injury to the operator, the track or its shipping crate.
Indeed, because continuous track drive units are so heavy, they can be damaged by their own weight if they are lifted improperly. Improper lifting can give rise to a stress point, and ultimately a stress concentration factor, at the point where the continuous track drive units are lifted. Furthermore, internal damage to the continuous track drive units can occur which are not visible to the eye, thereby creating further problems.
By far the greatest difficulty in handling continuous track drive units is during the installation of the track to a vehicle. Presently, rigging used to support and maneuver continuous track drive units is often inadequate because overhead clearance at multiple lift points is obstructed by the vehicle""s superstructure and other objects. Further, because vehicle track frames can be displaced only to a small increment, the continuous track drive unit must be installed in a nearly taut position prior to being placed over the idlers. Because there is no single point of balance and no inherent ability to stretch a track over the machine idlers, much time and effort is lost in attempting to lever the track onto the idlers, and the risk of injury to the operators is greatly increased. Further, such methods do not control sagging of the continuous track drive unit which binds and drags on every surface with which it comes in contact.
Yet another problem occurs when continuous track drive units are removed from the vehicle idlers. In order to facilitate removal, vehicle idlers can be displaced somewhat in order to loosen the tension of the track. The end idlers are composed of an inner and outer half, separated by a gap in which the cogs that are integrated into the inner surface of the track run captive, preventing lateral movement of the track on these idlers. The outer end idler halves are removed from the vehicle in order to free the track cogs during removal of the continuous track drive unit. Nonetheless, the weight of the track on the idlers often resists removal. Furthermore, at this point, it is difficult, to near impossible, to attach rigging to support the track such as chain, band slings, forklift tines or gripping clamps. Therefore, at that phase of removal, the track must be pulled and pried off the machine idlers by workers, thereby slowing down and complicating the process, to say nothing of the potential for human injury.
In view of the foregoing, there is a need for a method that overcomes the deficiencies in the prior art.
The present invention is a system and method to install and remove continuous track drive units on vehicles such as tractors, construction machinery and military vehicles. The present invention overcomes the problems associated with installation and removal of continuous track drive units including track damage, installation and removal speed, worker""s safety, and other collateral damages.
The present invention duplicates the shape and tensioning of the vehicle track frame to which the track will be installed. Two forcing discs, connected hydraulically, mimic the shape of the vehicle end idlers. A hydraulically actuated telescopic separator is positioned between the forcing discs, such that the discs may be separated or brought together. After aligning the forcing discs with the vehicle idlers, the continuous track drive unit may be easily slipped onto the vehicle idlers. The use of forcing discs of a diameter slightly larger than that of the vehicle end idlers facilitates the track installation operation by reducing friction between the track held taut on the present invention and the vehicle end idlers in their slack position.
Conversely, when removing continuous track drive units, the forcing discs are again aligned with the vehicle end idlers, and the track is slipped off the vehicle idlers and onto the forcing discs. The use of forcing discs somewhat smaller than the vehicle idlers is not necessary during the removal process, because clearance is developed on the low side of the track as the vehicle frame is detensioned, and the track sags away from the vehicle""s end idlers downward. This clearance created by gravity and the weight of the track is adequate to insert the present invention, in its slack state, into position.
An attachment hook allows the present invention to be positioned and aligned easily, and from one support point. Simply inverting the attachment hook allows the present invention to be used on either side of a vehicle having dissimilar diameter end idlers. Because the present invention can be made with lightweight materials, it not only reduces the time to install or remove a continuous track drive unit, but also reduces the number of workers needed to complete the operation. Indeed, the present invention allows installation and removal of continuous drive track units by only one man, one hoist, and one tool having some balance flexibility, minimal physical risk, minimal damage potential, and maximized speed and safety. Once the continuous track drive unit is removed from the vehicle idlers and onto the forcing discs, the present invention allows the track to be safely supported and easily repositioned.
It is therefore an object of the present invention to provide a new and improved continuous track drive unit installation system and method which has all the advantages of the prior art, yet none of the disadvantages.
It is another object of the present invention to provide a new and improved continuous track drive unit installation system and method which may be easily and efficiently manufactured and marketed.
It is a further object of the present invention to provide a new and improved continuous track drive unit installation system and method which is of durable and reliable construction.
It is even a further object of the present invention to provide a new and improved continuous track drive unit installation system and method which is susceptible of a low cost of manufacture with regard to both materials and labor, and which accordingly is then susceptible of low prices of sale to the consuming public, thereby making the present invention economically available to the buying public.
Yet another object of the present invention to provide a new and improved continuous track drive unit installation system and method which can be used with minimal space and effort.
The present invention may be better understood by referring to the following Detailed Description, which should be read in conjunction with the accompanying drawings. The Detailed Description of a particular and preferred embodiment, described below, is intended to be a particular example, and not a limitation.